Parameter support in rosserial?

I'm developing a rosserial node for reading some sensor values, and I was hoping to pull in a few parameters. There seems to be support in the code, and there's an old documentation page here (which isn't actually linked-to from the main documentation). This is my code:

I consistently get Tried to publish before configured, topic id 6, which is the parameter-fetch magic topic. I'm using Electric on an Oneiric system, with the rosserial debs. (I'm aware that I haven't got default values in here; I've removed those blocks, for simplicity of presentation.)